Personally, I always go with icon and text if I can. I will still use a plain icon with no text in a few cases and if it makes sense:

  •For the more universal ones like + and - and trashcans
  •If I am absolutely constrained for space and dont have time to redesign
  •If the target audience can handle it or knows it perhaps

I definitely agree that only icons is a bad design choice in most cases. I would go with plain text rather than a plain icon if I had to choose.